After searching google, and more frustration, I found: http://sebdah.github.com/blog/2012/10/02/debugging-jekyll/, Which explains I should do this, It gives error explainations, Which is best. secretly hidding error information is the worst thing you can do.

FelixMBPR:sunfmin.github.com sunfmin$ jekyll --no-auto --server
Configuration from /Users/sunfmin/Developments/sunfmin.github.com/_config.yml
Building site: /Users/sunfmin/Developments/sunfmin.github.com -> /Users/sunfmin/Developments/sunfmin.github.com/_site
ERROR: YOUR SITE COULD NOT BE BUILT:
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(<unknown>): found unexpected ':' while scanning a plain scalar at line 3 column 9 in /Users/sunfmin/Developments/sunfmin.github.com/_posts/2011-12-14-cannot-decode-object-of-class.md